When the Claude Code source code leaked on March 31, 2026 via a poorly secured npm .map file, most attention focused on the embarrassment for Anthropic. Less discussed: the malware campaigns that were already being built on top of that leak within hours.

As of today, threat actors are actively distributing Vidar infostealer malware and GhostSocks proxy through fake GitHub repositories designed to look like legitimate Claude Code forks. If you’ve been searching for Claude Code on GitHub in the last 48 hours, you may have encountered these repos.

What Happened

The Claude Code source code leaked on March 31. Within roughly 24 hours, threat actors had spun up fraudulent GitHub repositories mimicking the appearance of legitimate community forks. These repos:

  • Use plausible names like the now-identified idbzoomh account
  • Include fake README files with convincing install instructions
  • Deliver a payload that installs Vidar infostealer upon execution
  • May also install GhostSocks, a proxy tool used to route malicious traffic through victims’ connections

Vidar is a well-documented commodity infostealer sold on Russian-language cybercrime forums. It harvests:

  • Browser credentials and session tokens
  • Cryptocurrency wallet files
  • Saved passwords and autofill data
  • Discord tokens
  • Two-factor authentication codes (from authenticator apps)

For developers who work with AI tools, leaked credentials are particularly dangerous — API keys, GitHub tokens, and cloud provider credentials can result in catastrophic downstream damage.

Who Is at Risk

Any developer who:

  • Searched GitHub for “Claude Code” after March 31 and cloned an unverified repo
  • Ran install instructions from a community fork without verifying the source
  • Downloaded a .zip or binary labeled as Claude Code from an unofficial channel

Researchers at BleepingComputer, The Register, and MalwareTips have all confirmed the campaign is active as of today, April 2.

How to Protect Yourself

Immediate steps if you may be affected:

  1. Revoke credentials immediately — rotate any API keys, GitHub tokens, or cloud credentials stored in your browser or password manager
  2. Check for unknown processes — look for unusual background processes or network connections originating from recently installed software
  3. Scan with a trusted AV tool — run a full system scan with a reputable antivirus; Vidar leaves identifiable artifacts that most modern scanners detect
  4. Audit recent GitHub clones — review git remote -v output for any repos you cloned in the last 48 hours

Going forward:

  • Only download Claude Code from anthropic.com or the official Anthropic GitHub organization
  • Verify the GitHub repository owner — official Anthropic repos are under the anthropic organization, not personal accounts or community forks
  • Check commit history and contributor count — malware repos are usually fresh with 1–2 contributors and no meaningful commit history
  • Enable push protection and secret scanning on your own repos to prevent credential exposure

The Broader Pattern

This attack pattern — exploiting leaked or open-sourced AI tools to distribute malware through fake GitHub repos — is becoming increasingly common. It’s happened with:

  • Leaked Llama weights (2023)
  • Various Stable Diffusion forks
  • Earlier Cursor and Copilot-adjacent tools

The AI developer community tends to be early adopters who move fast, clone first, and audit later. Threat actors know this, and they’re timing their campaigns to exploit the window between a major AI news event and when security researchers publish their analyses.

What Anthropic Should Do

Anthropic has not issued an official statement specifically about the malware campaign as of this writing. The expected response would include:

  1. A security advisory published prominently at anthropic.com/security
  2. Coordination with GitHub to take down known malicious repos rapidly
  3. Guidance for developers who may have been affected

The original leak via the npm .map file also raises questions about Anthropic’s release security practices — but that’s a separate story.

Sources

  1. Claude Code leak used to push infostealer malware on GitHub — BleepingComputer
  2. Vidar infostealer campaign — The Register
  3. Claude Code malware analysis — MalwareTips

Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-20260402-2000

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